1. Field of Invention
The present invention relates generally to digital image capturing and processing scanners of ultra-compact design capable of reading bar code symbols in point-of-sale (POS) and other demanding scanning environments.
2. Brief Description of the State of Knowledge in the Art
The use of bar code symbols for product and article identification is well known in the art. Presently, various types of bar code symbol scanners have been developed for reading bar code symbols at retail points of sale (POS). In general, these bar code symbol readers can be classified into two (2) distinct classes.
The first class of bar code symbol reader uses a focused light beam, typically a focused laser beam, to sequentially scan the bars and spaces of a bar code symbol to be read. This type of bar code symbol scanner is commonly called a “flying spot” scanner as the focused laser beam appears as “a spot of light that flies” across the bar code symbol being read. In general, laser bar code symbol scanners are sub-classified further by the type of mechanism used to focus and scan the laser beam across bar code symbols.
The second class of bar code symbol readers simultaneously illuminate all of the bars and spaces of a bar code symbol with light of a specific wavelength(s) in order to capture an image thereof for recognition and decoding purposes.
The majority of laser scanners in the first class employ lenses and moving (i.e. rotating or oscillating) mirrors and/or other optical elements in order to focus and scan laser beams across bar code symbols during code symbol reading operations. Examples of hand-held laser scanning bar code readers are described in U.S. Pat. Nos. 7,007,849 and 7,028,904, each incorporated herein by reference in its entirety. Examples of laser scanning presentation bar code readers are described in U.S. Pat. No. 5,557,093, incorporated herein by reference in its entirety. Other examples of bar code symbol readers using multiple laser scanning mechanisms are described in U.S. Pat. No. 5,019,714, incorporated herein by reference in its entirety.
In demanding retail environments, such as supermarkets and high-volume department stores, where high check-out throughput is critical to achieving store profitability and customer satisfaction, it is common for laser scanning bar code reading systems to have both bottom and side-scanning windows to enable highly aggressive scanner performance. In such systems, the cashier need only drag a bar coded product past these scanning windows for the bar code thereon to be automatically read with minimal assistance of the cashier or checkout personal. Such dual scanning window systems are typically referred to as “bioptical” laser scanning systems as such systems employ two sets of optics disposed behind the bottom and side-scanning windows thereof. Examples of polygon-based bioptical laser scanning systems are disclosed in U.S. Pat. Nos. 4,229,588; 4,652,732 and 6,814,292; each incorporated herein by reference in its entirety.
Commercial examples of bioptical laser scanners include: the PSC 8500—6-sided laser based scanning by PSC Inc.; PSC 8100/8200, 5-sided laser based scanning by PSC Inc.; the NCR 7876—6-sided laser based scanning by NCR; the NCR7872, 5-sided laser based scanning by NCR; and the MS232x Stratos®H, and MS2122 Stratos® E Stratos 6 sided laser based scanning systems by Metrologic Instruments, Inc., and the MS2200 Stratos®S 5-sided laser based scanning system by Metrologic Instruments, Inc.
In general, prior art bioptical laser scanning systems are generally more aggressive that conventional single scanning window systems. However, while prior art bioptical scanning systems represent a technological advance over most single scanning window system, prior art bioptical scanning systems in general suffer from various shortcomings and drawbacks. In particular, the scanning coverage and performance of prior art bioptical laser scanning systems are not optimized. These systems are generally expensive to manufacture by virtue of the large number of optical components presently required to construct such laser scanning systems. Also, they require heavy and expensive motors which consume significant amounts of electrical power and generate significant amounts of heat.
In the second class of bar code symbol readers, early forms of linear imaging scanners were commonly known as CCD scanners because they used CCD image detectors to detect images of the bar code symbols being read. Examples of such scanners are disclosed in U.S. Pat. Nos. 4,282,425, and 4,570,057; each incorporated herein by reference in its entirety.
In more recent times, hand-held imaging-based bar code readers employing area-type image sensing arrays based on CCD and CMOS sensor technologies have gained increasing popularity.
In U.S. patent application Ser. No. 10/712,787, a detailed history of hand-hand imaging—based bar code symbol readers is provided, explaining the many problems that had to be overcome to make imaging-based scanners competitive against laser-scanning based bar code readers. Metrologic Instruments' Focus® Hand-Held Imager is representative of an advance in the art which has overcome such historical problems. An advantage of 2D imaging-based bar code symbol readers is that they are omni-directional by nature of image capturing and processing based decode processing software that is commercially available from various vendors.
U.S. Pat. No. 6,766,954 to Barkan et al. proposes a combination of linear image sensing arrays in a hand-held unit to form an omni-directional imaging-based bar code symbol reader. However, this hand-held imager has limited application to 1D bar code symbols, and is extremely challenged in reading 2D bar code symbologies at POS applications.
And yet despite the increasing popularity in area-type hand-held and presentation type imaging-based bar code symbol reading systems, such systems still cannot complete with the performance characteristics of conventional laser scanning bioptical bar code symbol readers in POS environments.
Thus, there is a great need in the art for an improved bar code symbol reading system that is capable of competing with conventional laser scanning bioptical bar code readers employed in demanding POS environments, and providing the many advantages offered by imaging-based bar code symbol readers, while avoiding the shortcomings and drawbacks of such prior art systems and methodologies.